Instrument For Guiding Stage Apparatus And Method For Using Same

ABSTRACT

This documents describes among other things a normalizing stage apparatus, tools and methods. One example includes a base that defines a trajectory. A first stage is moveably coupled to the base and the first stage moves along the trajectory. A second stage is moveably coupled to the first stage and moves an instrument coupled thereto with respect to the base and the first stage. Before movement of the instrument, the first and second stages are in first positions desired (e.g. predetermined) distances from a target area in the body. Another example includes the first stage and a guide tube stop coupled with the first stage. A guide tube is coupled with the guide tube stop and extends through a guide tube stop lumen. The guide tubes outer perimeter is dimensioned and configured to snugly couple with the surface defining the guide tube stop lumen.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.11/005,607 filed on Dec. 4, 2004. The entire disclosure of the aboveapplication is incorporated herein by reference.

This application also relates to Ser. No. 11/005,605 filed on Dec. 4,2004, entitled “MULTI-LUMEN INSTRUMENT GUIDE,” the disclosure of whichis also incorporated herein by reference in its entirety.

FIELD

The present disclosure relates generally to a stage from whichinstruments are positioned and in particular to a stage that provides aknown distance from the stage to a target.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

Neurosurgery sometimes involves inserting an electrode such as arecording or stimulating electrode (for recording brain signals orproviding stimulating pulses), or other instrument (for example, acatheter for fluid aspiration or drug infusion) through a burr hole orother entry portal into a subject's brain towards a target region of thebrain. The present inventors have recognized an unmet need fornormalizing stage devices, tools, and methods that provide a knowndistance between a stage and a target, such as to reduce or avoidphysician and technician calculations and equipment adjustments.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is a perspective view illustrating one embodiment of anormalizing stage and trajectory guide.

FIG. 2 is a perspective view of one embodiment of the normalizing stage.

FIG. 3 is another perspective view of one embodiment of the normalizingstage.

FIG. 4 is a top view of one embodiment of the normalizing stage.

FIG. 5 is a perspective of one embodiment of the normalizing stage.

FIG. 6 is a rear view of another embodiment of the normalizing stagehaving a potentiometer.

FIG. 7 is a side view of yet another embodiment of the normalizing stagehaving a hydraulic system.

FIG. 8 is a sectional view of yet another embodiment of the normalizingstage.

FIG. 8B is a sectional view of a further embodiment of the normalizingstage.

FIG. 8C is a perspective view of an embodiment of the first portion of asecond stage.

FIG. 8D is a perspective view of one example of a first stage and asecond portion of the second stage of the normalizing stage.

FIG. 8E is a perspective view of one example of the first stage and thefirst portion of the second stage of the normalizing stage.

FIG. 9 is a side view illustrating the fluid inlet and syringe used tofill the hydraulic system, as well as the master cylinder and masterpiston.

FIG. 10A is a sectional view illustrating an embodiment of a normalizingstage having another hydraulic system.

FIG. 10 B is a section view illustrating another example of the fluidinlet and syringe, as well as another example of the master cylinder andmaster piston.

FIG. 11 A is an exploded view of a fixture assembly illustrating a skullsurface, instrument immobilizer, trajectory guide, and an alignmentring.

FIG. 11B is an exploded view of a fixture assembly illustrating a skullsurface, instrument immobilizer, trajectory guide, and another exampleof an alignment ring.

FIG. 12 is an exploded view of a fixture assembly including thetrajectory guide, alignment ring, centered alignment guide, andorienting fixture.

FIG. 13 is an exploded view of a fixture assembly including thetrajectory guide, alignment ring, offset alignment guide, and theorienting fixture.

FIG. 14 is a partial section and exploded view of a fixture assemblyincluding the trajectory guide, alignment ring, and centered instrumentguide.

FIG. 15 is a partial section and exploded view of a fixture assemblyincluding the trajectory guide, alignment ring, and offset instrumentguide.

FIG. 16A is an exploded view showing the normalizing stage, guide tubestop, guide tube, and obturator.

FIG. 16B is an exploded view of the guide tube stop.

FIG. 17 is a perspective view showing the normalizing stage, guide tubestop, guide tube, spacer tube, instrument retaining assembly, and aninstrument.

FIG. 18 is a front view of a bracket assembly including the bracket,measurement tube, and an instrument.

FIG. 19 is a perspective view showing the normalizing stage, guide tubestop, guide tube, spacer tube, instrument, instrument guide, trajectoryguide, and instrument immobilizer coupled to the skull.

FIG. 20 is a perspective view showing the normalizing stage, guide tubestop, guide tube, bracket, instrument, instrument guide, trajectoryguide, and instrument immobilizer coupled to the skull.

FIG. 21 is a perspective view showing the normalizing stage, bracket,instrument guide, instrument immobilizer, trajectory guide, instrument,guide tube stop, and guide tube in an intermediate position.

FIG. 22 is a perspective view showing the normalizing stage, bracket,instrument guide, guide tube stop, guide tube, trajectory guide,instrument, and the instrument immobilizer engaged to the instrument.

FIG. 23 is a perspective view showing the instrument immobilizer, aninstrument bent over, and a cap engaged to the instrument immobilizer.

FIG. 24 is a block diagram showing generally an example for using anormalizing stage apparatus and attendant devices.

FIG. 25 is a block diagram showing in more detail an example forcoupling a fixing assembly to the skull.

FIG. 26 is a block diagram showing in more detail an example fordetermining a position of the moveable stage of the normalizing stageapparatus relative to a desired target area.

FIG. 27 is a block diagram showing in more detail an example forplunging and advancing an instrument to the desired target area.

FIG. 28 is a block diagram showing in more detail an example forplunging another instrument to the desired target area.

FIG. 29 is a block diagram showing in more detail an example forimmobilizing the other instrument and removing the normalizing stageapparatus and fixing assembly.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings.

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof, and in which is shown byway of illustration specific embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those skilled in the art to practice the invention, and it is tobe understood that the embodiments may be combined, or that otherembodiments may be utilized and that structural, logical and electricalchanges may be made without departing from the scope of the presentinvention. The following detailed description is, therefore, not to betaken in a limiting sense, and the scope of the present invention isdefined by the appended claims and their equivalents.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one. Furthermore, allpublications, patents, and patent documents referred to in this documentare incorporated by reference herein in their entirety, as thoughindividually incorporated by reference. In the event of inconsistentusages between this documents and those documents so incorporated byreference, the usage in the incorporated references(s) should beconsidered supplementary to that of this documents; for irreconcilableinconsistencies, the usage in this document controls.

FIG. 1 is a perspective view illustrating generally a normalizing stageapparatus 100 for positioning an instrument using a stage positioned ata known desired (e.g., predetermined) distance from a target. In oneexample, the target is a location in a brain. The normalizing stageapparatus 100 is coupled to a patient through a fixture assembly 102,sometimes referred to as a trajectory guide. The fixture assembly 102 isoperable to position the normalizing stage 100 in a desired orientationto provide a fixable desired trajectory to the target.

FIG. 2 is a front perspective view of a portion of the normalizing stage100, which includes a base 200. In this example, an inner surface of thebase 200 defines a socket 202, for an instrument guide (describedbelow). A thumb screw 204 or other fixation devices extends through thebase 200 and into the socket 202, in this example. The thumb screw 204is operable to engage an instrument guide and fixedly couple thenormalizing stage 100 to the instrument guide. The base 200 furtherincludes guide rails 206A, 206B that extend from a lower portion 208.The longitudinal axis of the socket 202 defines a trajectory 228. Theguide rails 206A, 206B are substantially parallel to the trajectory 228defined by the socket 202. In this example, one of the guide rails 206Bhas a “T” cross section and the remaining guide rail 206A has anapproximately rectangular cross section. In another example, the guiderails 206A, 206B both have approximately rectangular cross sections orother geometries that allow for slidable movement along the guide rails206A, 206B.

A first stage 210 is coupled to the guide rails 206A, 206B. In thisexample, the first stage 210 includes a lower portion 222 and upperportion 224. The first stage 210 includes four guide rail lumens, twoguide rail lumens 212A, 212B extend through the lower portion 222 andanother two guide rail lumens 212C, 212D extend through the upperportion 224. The guide rail lumens 222 are dimensioned and configured toslidably couple with the guide rails 206A, 206B. This enables movementof the first stage 210 along the trajectory 228 defined by the socket202. Additionally, the span 230 between the upper guide rail lumens212C, 212D and lower guide rail lumens 212A, 212B aids in preventingunwanted lateral or rotational translation of the stage 210 with respectto the trajectory 228. In other words, the sliding relationship of theguide rails 206A, 206B to the guide rail lumens 212A, B, C, D of thefirst stage 210 constrains lateral movement of the first stage withrespect to the trajectory 228, while allowing movement along thetrajectory. A thumb screw 214 or other fixation device extends through aportion of the first stage 210 and into the guide rail lumens 212B. Thethumb screw 214 is operable to engage one of the guide rails 206A, 206Band immobilize the first stage with respect to the base 200. The firststage 210 also includes a lumen 216. The lumen 216 is substantiallyaligned with the socket 202. When the first stage 210 is advanced alongthe trajectory 228 the lumen 216 remains aligned with the trajectory228.

FIG. 3 is a rear perspective view of the same portion of the normalizingstage 100 including three scales 316A-C. A first stage actuator 300,comprising a knob in this example, is coupled to the first stage 210. Inthis example, a stationary screw 302 is coupled to the base 200. In thisembodiment, the stationary screw 302 extends through and is coupled tothe first stage actuator 300. The stationary screw 302 is also coupledto the first stage 210. In this example, the stationary screw 302 issubstantially parallel to the trajectory 228 (FIG. 2). The first stageactuator 300 is operable to advance the first stage 210 along thetrajectory 228 by rotating the actuator 300. The first stage actuator300 includes threads on an inner surface which engage correspondingthreads of the stationary screw 302. The stationary screw 302 is longenough to enable a desired position of the first stage 210 with respectto the desired target of substantially all subjects into which aninstrument is to be introduced.

In this embodiment a scale 304 is provided, such as along a side of thefirst stage 210 near a guide rail 206B. The scale 304 is graduated toindicate a range of positions of the first stage 210 with respect to adesired target. A reference mark 306 on a guide rail 206B is positionedto cooperatively indicate, with the graduated scale 304 on the firststage 210, the position of the first stage with respect to the target.

Referring again to FIG. 2, a second stage 218 is movably coupled to thefirst stage 210. In one example, the second stage 218 is coupled to thefirst stage 210 by a screw 220 or the like. The screw 220 extendsbetween the lower portion 222 and upper portion 224 of the first stage210 and is rotatably coupled to each. The second stage 220 includes alumen having inner threads engaging the threads for screw 220.Additionally, the second stage 218 includes a retaining assembly orifice226 dimensioned and configured to couple with a retaining assembly, asdescribed below. In this example, the retaining assembly orifice 226 isa broken ring. In another example, the retaining assembly orifice 226 isdefined by a continuous inner surface of the second stage 218. A thumbscrew 232 or other fixation device is coupled to and extends through aportion of the second stage 218. The thumb screw 232 is operable toimmobilize an instrument extending through the retaining assembly lumen226.

FIG. 3 is a perspective view of the normalizing stage 100 As shown inthe example illustrated in FIG. 3, an actuator knob 308 is coupled tothe first stage 210. The actuator knob 308 is connected by cooperativegearing to the screw 220 (FIG. 2), in this example. The knob 308 is thusoperable to move the second stage 218 along the screw 220. Additionallyin this example, the second stage 218 includes a protrusion 310 whichextends from a surface of the second stage through a slot 312 in thefirst stage 210. The protrusion 310 maintains the alignment of thesecond stage 218 to the first stage 210 during rotation of the knob 308,which turns the screw 220. Specifically, the slot 312 helps theretaining assembly orifice 226 to remain aligned with the guide tubestop lumen 216 and instrument guide lumen 202.

In the example shown in FIG. 3, the protrusion 310 also includes areference marking 314. The reference marking 314 indicates the positionof an instrument with respect to the standardized distance to target. Inone example, a scale 316A-C is included on the first stage 210. Thescale 316A-C is disposed adjacent to the slot 312. In one example, thereference marking 314 is read against the scale 316A to determine theposition of the instrument with respect to the target. Optionally, thescale 316A and marking 314 show the position of a tip of the instrumentwith respect to the target. In another example, scale 316B is includedon the first stage 210 in place of scale 316A. Scale 316B in cooperationwith the marking 314 has the “0” of the scale 316B corresponding to thetop of the travel of the second stage 218. Scale 316C, in yet anotherexample, cooperates with marking 314 so the “0” of the scale 316Ccorresponds to an approach distance remote from the desired target. As aresult, when the mark 314 is located at the “0” of the scale 316C thetip of the instrument is positioned a desired (e.g., predetermined)approach distance (e.g. 15 millimeters) from the desired target. Instill another example, the scales 316A-C are adjustable (for example,removable and reattachable, such as with an adhesive backing) and ispositioned along the slot 312 according to the needs of the physician ortechnician. The mark 314 is part of a vernier scale 318, in anotheroption, and the vernier scale 318 provides another degree of precisionfor measuring the distance from the instrument to the desired target.

FIG. 4 is a top view of one embodiment of the normalizing stage 100. Acircular fine scale 400 is coupled to the top of the screw 220. Thescrew 220 is threaded. Each rotation of the screw 220 correspond to onerotation of the fine scale 400. In one example, one rotation of thescrew 220 moves the second stage 218 by 1 mm toward or away from thetarget. In this example, the fine scale 400 is graduated so one rotationof the scale indicates 1 mm of advancement, and 0.1 mm and 0.01 mmincrements are also indicated. A reference marking 402 is included onthe first stage 210 to indicate the position of the second stage 218when reading the fine scale 400. The scale 400, in one option, includesan inner scale 404 and an outer scale 406. The inner scale 404 is usedto measure translation of the second stage 218 from the “0” marking onscale 316A, 316C to a measure above “0” in another option (e.g. from10.6 millimeters to 10.7 millimeters above “0”). In yet another option,the outer scale 406 is used to measure translation of the second stage218 from the “0” marking on the scale 316A, 316C to a measure below “0”,for instance from 4.0 millimeters to 4.1 millimeters below “0.” As aresult, the inner scale 404 is used to measure translation of the secondstage 218 above “0” and the outer scale 406 is used to measuretranslation of the second stage 218 below “0.”

FIG. 5 is a bottom perspective view of one embodiment of the normalizingstage 100. The socket 202 includes keyed slots 500 or the like withinthe base 200. When the normalizing stage 100 is coupled to an instrumentguide (described below), the surfaces defining the keyed slots 500engage corresponding keys present on the instrument guide. Unwantedrotation of the normalizing stage 100 is thus prevented with respect tothe instrument guide.

FIG. 6 is a rear view of another embodiment of the normalizing stage100. In this embodiment, the position of the second stage 218 withrespect to the first stage 210 is measured by a potentiometer assembly600. The assembly 600 includes a wiper 602. In this example, the wiper602 is coupled to the second stage 218. Alternatively, the wiper 602 iscoupled to the first stage 210. The wiper 602 electrically contacts andbridges between two elongate resistors 604 physically parallel to oneanother and coupled to the first stage 210. The resistors 604 are ofsufficient length to enable the second stage 218 to advance aninstrument toward, away, and/or through a target while still contactingthe wiper 602 to measure the position of the second stage 218. In oneexample, a cable 606 connects the potentiometer assembly 600 to anoutput device that includes a display screen. The output device displaysthe location of the second stage 218 according to the position of thewiper 602 with respect to the resistors 604. In another example, theoutput device displays the location of an instrument with respect to adesired target in a similar manner as with the scales 316A-C (describedabove). In an alternate example, the resistors 604 are coupled to thesecond stage 218 and the wiper 602 is coupled to the first stage 210. Inanother option, supplemental resistors are coupled to the base 200 orthe first stage 210 and a supplemental wiper is coupled to the other ofthe base 200 or the first stage 210. As a result, a potentiometerassembly is used to measure translation of the first stage 210 withrespect to the base 200.

FIG. 7 illustrates a side view of another embodiment of the normalizingstage 100 that includes a hydraulic system 700. The hydraulic system 700includes, in fluid communication with each other, a hydraulic cylinder702, hydraulic piston 704, master hydraulic cylinder 706, and masterhydraulic piston 708. The master hydraulic cylinder 706 and piston 708are operable to actuate the hydraulic cylinder 702 and piston 704. Inone example, the hydraulic cylinder 702 and piston 704 move the secondstage 218 with respect to the first stage 210.

FIG. 8A is a cross section view of the hydraulic embodiment of thenormalizing stage 100. In this example, the hydraulic cylinder 702 ismounted to the first stage 210 and the hydraulic piston 704 is mountedto the second stage 218 (or vice versa). In this example, the hydraulicpiston 704 is coupled to the second stage 218 by a piston tube 800. Inone example, a hydraulic line 802 coupled to the master piston 708 (FIG.7) extends through the piston tube 800 and is coupled substantiallyadjacent to the hydraulic piston 704. In another example, the hydraulicline 802 is coupled to the piston tube 800 at any location along thelength of the piston tube 800. In yet another example, the hydraulicline 802 is coupled to the second stage 218 and in fluid communicationthrough a coupling to the piston tube 800. The inner surface of thehydraulic cylinder 702 and hydraulic piston 704 define a first volume804. The first volume 804 is increased and decreased by actuation of themaster cylinder 706 and master piston 708. Changing the first volume 804advances the piston 704 inside the cylinder 702, which, in turn,advances the second stage 218.

In the example shown in FIG. 8A, a spring housing 806 is coupled to thefirst stage 210. In this example, the housing 806 is a tubularstructure. A spring 808 or the like is coupled to one end of the housing806, in one example. The other end of the spring 808 is coupled to thesecond stage 218. In another example, an elastic material, for examplean elastomeric membrane is coupled between the housing 806 and thesecond stage 218. The spring 808 is in tension and maintains a force onthe second stage 218. In other words, the spring 808 pulls the secondstage 218 and the hydraulic piston 704 toward the fluid filled end ofthe hydraulic cylinder 702. The incompressibility of hydraulic fluid inthe hydraulic cylinder 702 prevents the spring 808 from undesirablyadvancing the second stage 218. The spring 808 thus maintains apressurized hydraulic system 700 by pulling the piston 704 toward thecylinder 702. In this example a stopcock valve 810 or the like iscoupled to the hydraulic cylinder 702 and is in fluid communicationthereto.

The second stage 218, shown in FIG. 8A, is slidably mounted on andguided by a guide rail 812 associated with the first stage 210. Guidesurface 814 of the second stage 218 provides smooth linear motion ofsecond stage 218 along an interface 816 with the guide rail 812. Guidesurface 814, in one example is integral with the second stage 218 (FIG.8A). In another example, guide surface 814 includes a friction-reducinginsert or coating made of a bearing material, including but not limitedto, TEFLON. Optionally, the coating or insert is coupled along the guiderail 812.

Another example of the normalizing stage 100 is shown in FIG. 8B. Thesecond stage 218 includes at least one recirculating bearing 818including ball bearings 820. The recirculating bearing 818 is at theinterface 816 between the second stage 218 and guide rail 812 andthereby reduces friction first and second stages 210, 218. As shown inFIG. 8B, the recirculating bearing is a linear bearing to permit linearmovement along the guide rail 812. In another example, the bearing 818is a conventional non-circulating type. In yet another example, therecirculating bearing 818 is a flat bearing that rides along the guiderail 812. The guide rail 812 includes at least one groove 822 forreceiving the balled bearings 820 of the flat recirculating bearing 818to align the second stage 218 and thereby prevent undesired rotation ofthe second stage 218 around the guide rail 812. In still anotherexample, the recirculating bearing 818 is a round bearing having acircular inner perimeter at the interface 816. Optionally, the secondstage 218 includes a pair of round recirculating bearings 818 that rideon dual guide rails 812 to prevent undesired rotation of the secondstage 218. The bearings 818 substantially reduce friction at theinterface 816 thereby facilitating increased responsiveness of thesecond stage to actuation with the hydraulic actuator (e.g., the masterhydraulic cylinder 706 and the master hydraulic piston 708).

In another example, a gas vent 824 is substituted for the valve 810. Thegas vent 824 is coupled to the hydraulic cylinder 702 and in fluidcommunication thereto. When the hydraulic system 700 is filled (asdescribed below) hydraulic fluid fills the volumes defined by thecylinders 702, 706, pistons 704, 708 and the hydraulic line 802. The airor other gas present in these spaces is forced out by introduction ofthe fluid. The valve 810 or gas vent 824 permits the gases to escapefrom the hydraulic system 700, but retains the hydraulic fluid therein.While gas permeable, the gas vent 824 is not liquid permeable. In oneexample, the gas vent 824 is a membrane comprised ofpolytetrafluoroethylene sold under the trademark TEFLON. In anotherexample, any liquid impermeable membrane that otherwise is gas permeableis used as the gas vent 824.

FIGS. 8C-E illustrate another example of bearings coupled between thefirst stage 210 and the second stage 218. One example of a first portion825 of the second stage 218 including three rollers 826 (e.g., needlerollers) is shown in FIG. 8C. In another example, the second stage 218includes one or more rollers 826 (e.g., eight needle rollers). Therollers 826 are coupled to the first portion 825 with axles 827 thatpermit rotation of the rollers 826. The axles 827 have a small diameterto decrease bearing friction between the rollers 826 and the firstportion 825. The first portion 825 of the second stage 218 shown in FIG.8C is sized and shaped to couple along one side of the guide rails 812(FIGS. 8D, E). Optionally, as shown in FIG. 8D, a second portion 828 ofthe second stage 218 having rollers 826 (FIG. 8E) is sized and shaped tocouple along an opposed side of the guide rails 812 relative to thefirst portion 825. The first and second portions 825, 828 are coupledtogether, in one example, with fasteners 830 (FIG. 8D, E) such asscrews, rivets, mechanical fittings and the like.

FIGS. 8C-E show one example of how the rollers 826 are arranged aroundthe guide rails 812 to permit linear movement of the second stage 218with substantially reduced friction. As shown in FIGS. 8D, E the guiderails 812 are sized and shaped to contact the rollers 826 of the firstand second portion 825, 828 at angles intended to limit the movement ofthe second stage 218 to linear movement along the guide rails 812. Thefirst and second portions 825, 828 of the second stage 218 arecorrespondingly sized and shaped to position the rollers 826 along theangled surfaces of the guide rails 812. Importantly, the arrangement ofthe rollers 826 allows linear movement of the second stage 218, butotherwise prevents unwanted rotation of the second stage 218 around theguide rails 812. In another example, the guide rails 812 and the firstand second portions 825, 828 are sized and shaped in a variety oforientations that cooperate to permit linear movement of the secondstage 218 without allowing rotation around the guide rails 812. Forexample, four rollers are positioned at angles relative to each otheraround a guide rail. Optionally, additional rollers are provided toenhance reduction of friction while allowing linear movement of thesecond stage 218 relative to the first stage 210.

FIG. 9 is a side view illustrating a fluid inlet 900 and syringe 902used to fill the hydraulic system 700. In this example, the fluid inlet900 is coupled to the master hydraulic cylinder 706 and is in fluidcommunication thereto through a manifold 908 that includes a portion ofthe hydraulic line 802, which is also in fluid communication with themaster hydraulic cylinder 706. In another example, the fluid inlet 900is in direct fluid communication with the master hydraulic cylinder 706.The fluid inlet 900 includes a socket 904 and check valve 906. The checkvalve 906 prevents fluid introduced at the inlet 900 from leaking out atthe inlet 900. In the example shown in FIG. 9, a stopcock 912 is coupledto the check valve 906 and in fluid communication thereto. The syringe902 includes a nozzle 910 dimensioned and configured to snugly couplewith the socket 904 of the fluid inlet 900. The syringe 902 is filledwith a hydraulic fluid (for example, sterile saline) and the nozzle 910is inserted into and coupled to the socket 904. The plunger 915 of thesyringe 902 is then depressed. This forces the hydraulic fluid from thesyringe 902 into the fluid inlet 900 and hydraulic system 700. In oneexample, the syringe 902 injects enough hydraulic fluid into the system700 to fill the volume defined by the cylinders 702, 706, pistons 704,708, and hydraulic line 802 and allow a full range of movement for thesecond stage 218. In another example, the syringe 902 is filled and usedmultiple times to fully fill the hydraulic system 700.

The master hydraulic cylinder 706 and master hydraulic piston 708 areshown in FIG. 9. As described above, the master hydraulic piston 708 iscoupled to the master hydraulic cylinder 706 to allow slidable movementtherebetween. The inner surface of the master cylinder 706 and themaster piston 708 define a second volume 914. The second volume isincreased and decreased by actuation of a screw 916, a distal end ofwhich is coupled to the master piston 708 and the master cylinder 706.The threaded outer surface of the screw 916 engages a correspondinglythreaded inner surface of the master cylinder 706. Rotation of the screw916 advances the screw, and thus the master piston 708, with respect tothe master cylinder 706. A knob 918 is coupled to a proximal end of thescrew 916 to enable rotation of the screw. Changing the second volume914 correspondingly changes the first volume 804 in a substantiallyinverse manner by moving hydraulic fluid through the hydraulic line 802.In other words, decreasing the second volume 914 similarly increases thefirst volume 804, and increasing the second volume decreases the firstvolume in substantially the same way. The screw 916 thus operates tomove the second stage 218 through actuation of the master cylinder 706,master piston 708, hydraulic cylinder 702, and hydraulic piston 704.

FIG. 10A is a sectional view of another embodiment of normalizing stage100 including a rolling diaphragm hydraulic system 1000. In thisexample, hydraulic system 1000 includes a piston 1002 disposed within acylinder 1004. In one example, a flexible fluid impermeable membrane1006 extends from a surface defining the circumference of piston 1002.The membrane 1006 is coupled to the cylinder 1004. The membrane 1006,piston 1002, and cylinder 1004 define a first volume 1008. The firstvolume 1008 is changed by actuation of the master piston 708 and mastercylinder 706 via screw 916 (described above). The flexible membrane 1006provides a seal between the cylinder 1004 and piston 1002 while onepiece moves with respect to the other. In an example, there issufficient clearance between the cylinder 1004 and piston 1002 for theflexible membrane to fold between the cylinder and piston. In otherwords, the cylinder 1004 and piston 1002 move without directlycontacting one another. Expanding and contracting the first volume 1008thereby produces substantially little friction between cylinder 1004 andpiston 1002. Thus, more accurate and responsive movement of the piston1002 with respect to the cylinder 1004 is possible.

In one example, a spring 1014 or the like is disposed between piston1002 and cylinder 1004. The spring 1014 is optionally in compression andmaintains a force on the piston 1002 relative to the cylinder 1004. Thespring 1014 pushes piston 1002 and, with it, second stage 218 toward thefluid filled end of the cylinder 1004. The incompressibility ofhydraulic fluid in the cylinder 1002 prevents the spring 1014 fromundesirably moving the second stage 218. The spring 1014 thus maintainsa pressurized hydraulic system 1000 by pushing the piston 1002 towardthe cylinder 1004.

Referring now FIG. 10B, in another example, a flexible liquidimpermeable membrane 1018 for a rolling diaphragm extends between themaster hydraulic cylinder 706 and master hydraulic piston 708. Themaster hydraulic piston 708 is coupled to master hydraulic cylinder 706with a rolling diaphragm similarly to how piston 1002 and cylinder 1004are coupled in FIG. 10. The rolling diaphragm provided with the flexiblemembrane 1018 facilitates enhanced movement of the piston 708 relativeto the cylinder 706 by reducing friction therebetween. Additionally, thereduced friction provided by the flexible membrane 1018 improvesresponsiveness between rotation of the knob 918 and movement of thepiston 708 thereby enhancing overall responsiveness at the piston 1002and the cylinder 1004 of the normalizing stage 100 (FIG. 10).

In yet another example shown in FIG. 10B, the syringe 902 and stopcock912 couple to hydraulic line 802 between hydraulic system 1000 and themaster hydraulic system 700. Coupling the fluid inlet 900 provided bythe syringe 902 and the stopcock 912 along the line 802 eliminates theneed for the manifold 908 (FIG. 9). Additionally, the fluid inlet 900 isin closer communication with the hydraulic system 1000 facilitatingeasier filling of the system 1000.

An inlet 1010 to the first volume 1008 is provided through the cylinder1004. The inlet 1010 and the first volume 1008 are in fluidcommunication with the hydraulic line 802. A stopcock valve 1012 iscoupled to the cylinder 1004 and is operable to open or seal the system1000 for hydraulic fluid filling.

As described in a previous example, a gas vent can be substituted forstopcock valve 1012 in FIG. 10. In this example, as before, air or othergas in first volume 1008 escapes through the gas permeable membrane ofthe vent. In one example, end surface 1016 of cylinder 1004 is replacedwith a suitably-supported gas permeable membrane. Because hydraulicsystem 1000 is under pressure relative to the surrounding atmosphere(e.g., due to spring 1014), gas or air bubbles are forced out of thehydraulic fluid when they contact the surface of the membrane. The largesurface area and direct path at the end surface 1016 facilitate theescape of gas or air from within the hydraulic system 1000. In this way,hydraulic system 1000 easily fills completely with incompressiblehydraulic fluid (e.g., sterile saline). In another example, bothhydraulic system 1000 and the master hydraulic system 700 include gasvents as just described.

The position of the second stage 218 relative to the first stage 210, inone example including the hydraulic systems 700, 1000, is measured witha potentiometer, such as potentiometer assembly 600 (described above).The potentiometer assembly 600 provides accurate and precise indicationsof the second stage 218 position with respect to the first stage 210. Inanother example, the potentiometer assembly 600 indicates the positionof an instrument with respect to the desired target (as describedabove). The potentiometer assembly 600 allows for direct measurement ofmovement of the second stage 218 relative to the first stage 210. Thepotentiometer assembly 600 overcomes measurement error due to lag orhysteresis caused by deformability of the materials used in thehydraulic systems 700, 1000. Measurement error typically appears whenmeasuring the position of the hydraulic pistons 704, 1002 relative tothe hydraulic cylinders 702, 1002 by translation of the master piston708 relative to the master cylinder 706. The potentiometer assembly 600also overcomes measurement error caused by friction in the hydraulicsystems 700, 1000, for instance between the hydraulic cylinders 702,706, 1004 and hydraulic pistons 704, 708, 1002. Measurement error isovercome by directly measuring the translation of the second stage 218relative to the first stage 210 with the potentiometer assembly 600.

FIG. 11A is an exploded view of a portion of the fixture assembly 102.An instrument immobilizer 1100 is coupled to the surface of a skull 1102around a burr hole in the skull 1102. In this example, the instrumentimmobilizer 1100 is coupled to the surface of the skull 1102 by bonescrews extending through the immobilizer and into the skull. Theimmobilizer 1100 further includes a retaining piece 1106. The retainingpiece 1106 is operable to engage and immobilize a portion of aninstrument (described below). Additional examples of instrumentimmobilizers are shown in PCT Patent Application No. PCT/US03/28966(Attorney Docket No. 723.066WO1) filed on Sep. 17, 2003, which isassigned to the assignee of the present patent application, and which isincorporated by reference herein in its entirety.

Additionally, in this example, a saddle assembly 1104 is coupled to theinstrument immobilizer 1100 and aligned with an orthogonal 1134 axisthrough a center of the instrument immobilizer 1100. Specifically, abase ring 1108 is coupled to the instrument immobilizer 1100. In oneexample, the saddle assembly 1104 is initially aligned with theorthogonal axis 1134, but coupled to the skull surface 1102. Theorthogonal axis 1134 is substantially orthogonal to the surface of theskull 1102. The saddle assembly 1104 further includes a cylindricalsectional tower base 1110 that is dimensioned and configured to couplewith the base ring 1108 to allow rotation therebetween. A saddle slide1112 is coupled to the tower base 1110. Thumbscrews 1114 or the likeextend through slots 1116 of the saddle slide 1112 and the tower base1110. The thumbscrews 1114 engage blocks 1118 disposed adjacent to thebase ring 1108. The blocks 1118 engage a lip of the base ring 1108. Thesaddle slide 1112 is operable to move in an arcuate motion with respectto the tower base 1110. In other words, the saddle slide 1112 rotates byrotating the tower base 1110 with respect to the base ring 1108 andsweeps an arc by moving the saddle slide 1112 with respect to the towerbase 1110. The saddle slide 1112 and the tower base 1110 are fixed inplace by tightening of the thumbscrews 1114, which pulls the blocks 1118against the base ring 1108, the base ring 1108 is pulled against thetower base 1110, and the tower base is pulled against the saddle slide.

The saddle assembly 1104 also includes a guide lumen 1120 having asaddle trajectory that passes through the base ring 1108 and theinstrument immobilizer 1100. The guide lumen 1120 is dimensioned andconfigured to interchangeably retain alignment guides and instrumentguides (described below). A thumbscrew 1122 or other fixation deviceextends through a wall of a cylindrical portion of the saddle slide 1112that defines the guide lumen 1120. The thumbscrew 1122 is operable toengage and retain an alignment guide or instrument guide having aportion disposed within the guide lumen 1120. The saddle slide 1112 ispositionable to orient the saddle trajectory in various orientationsavailable with the above described arcuate and rotational movement. Oneexample of the saddle assembly 1104 is further described in U.S. patentapplication Ser. No. 10/671,913 (Attorney Docket No. 723.061US1), filedon Sep. 25, 2003, which is assigned to the assignee of the presentapplication and which is incorporated by reference herein in itsentirety. Additional examples of saddles are shown in U.S. patentapplication Ser. No. 09/828,451 (Attorney Docket No. 723.031US1), filedon Apr. 6, 2001, which is assigned to the assignee of the present patentapplication, and which is incorporated by reference herein in itsentirety.

FIG. 11A also illustrates an alignment ring 1136 including tabs 1138.The tabs 1138 are sized and shaped to engage with a rack 1140 including,for instance teeth 1142. The teeth 1142, in one example, are spacedaround the rack 1140 at 4 degree intervals. The tabs 1138 deform withrotation of the alignment ring 1136 relative to the rack 1140 and snapinto the grooves between the teeth 1142 to provide a clicking detent.The alignment ring 1136, in another example, is thus incrementallypositionable around the rack 1140.

The alignment ring 1136 is sized and shaped to fit around the wall ofthe upwardly protruding cylindrical portion of the saddle slide 1112that defines the guide lumen 1120. Clamps 1144 extend from the alignmentring 1136, in another example. The rack 1140 projects radially, in yetanother example, from the cylindrical portion of the saddle slide 1112and defines a lip. The clamps 1144 are sized and shaped to engage withthe lip and secure the alignment ring 1136 to the saddle slide 1112 withinwardly extending hooks 1146, for example. The clamps 1144 deform asthe hooks 1146 are pressed over the rack 1140. The clamps 1144 assumethe undeformed shape when the alignment ring 1136 is pressed onto therack 1140 and hooks 1146 disengage from the rack 1140 and engage againstthe lip to secure the alignment ring 1136 to the saddle slide 1112. Aninner surface of the alignment ring 1136 defines grooves 1132dimensioned and configured to receive keyed teeth from an alignmentguide or instrument guide (both described below). In one example, thegrooves 1132 are positioned every 45 degrees about the inner surface ofthe alignment ring 1136.

FIG. 11B illustrates another example of an alignment ring 1124 includestwo semi-circular portions 1126. Each semicircular portion 1126 isdimensioned and configured to fit around the wall of the upwardlyprotruding cylindrical portion of the saddle slide 1112 that defines theguide lumen 1120. This wall includes an inward turned lip dimensionedand configured to engage a groove present in each semicircular portion1126. In one example, the lip and grooves have cooperatively engagedteeth, spaced approximately every 6 degrees of the 360 degreecylindrical wall. The semicircular portions 1126 are coupled to oneanother, such as with elastic bands 1128. The ends of the semicircularportions 1126 have pinching surfaces 1130 that extend from thesemicircular portions 1126. Each pair of pinching surfaces 1130 is nearone of the elastic bands 1128 on opposing sides of the elastic band1128. Pressure applied to opposed pinching surfaces 1130 stretches theelastic band 1128 and separates the semicircular portions 1126. In thisway the pinching surfaces 1130 are operable to spread the semicircularportions 1126 apart and allow rotational movement of the alignment ring1124 with respect to the saddle slide 1112. An inner surface of thealignment ring 1124 defines grooves 1132 dimensioned and configured toreceive keyed teeth from an alignment guide or instrument guide (bothdescribed below). In one example, the grooves 1132 are positioned every45 degrees about the inner surface of the alignment ring 1124.

FIG. 12 shows an exploded view of the fixture assembly 102 including thesaddle assembly 1104, alignment ring 1136, a centered alignment guide1200, and an orienting fixture 1202. The centered alignment guide 1200includes a base 1204 and an alignment pin 1206 coupled to the base. Inthis example, the alignment pin 1206 is centrally aligned with the base1204 such that when the centered alignment guide 1200 is inserted intothe lumen 1120 of the saddle assembly 1104, the pin 1206 is centeredwithin the lumen 1120 to define the saddle trajectory. The centeredalignment guide 1200 is immobilized within the lumen 1120 by thumbscrew1122 or the like. In one example, the centered alignment guide 1200includes keyed teeth 1208. The keyed teeth 1208 are dimensioned andconfigured to cooperatively engage the surfaces defining the grooves1132 of the alignment ring 1136. This prevents undesired rotationbetween the saddle assembly 1104 and the centered alignment guide 1200.In one example, the keyed teeth 1208 are disposed around thecircumference of the centered alignment guide 1200 at approximately 45degree intervals. In one example, the centered alignment guide 1200includes a flange 1210 that partially or completely circles acircumferential portion of the alignment guide 1200. The flange 1210engages the upper surface of the cylindrical wall of the saddle slide1112 that defines the guide lumen 1120. As a result, only the base 1204is within the guide lumen 1120 when the centered alignment guide 1200 iscoupled to the saddle assembly 1104.

The orienting fixture 1202 is coupled to the alignment pin 1206. In oneexample, a thumbscrew 1212 or other fixation device extends through aportion of the centered alignment guide base 1204 toward the alignmentpin 1206. The thumbscrew 1212 is operable to engage and retain theorienting fixture 1202 against the alignment pin 1206. In one example,the orienting fixture 1202 is remotely detectable such as by remotepositioning systems using infrared (IR) light detection. Such detectionuses a number of detectable objects on the orienting fixture 1202.Examples of such objects include reflective structures or light emittingdiodes (LED's) included on the orienting fixture 1202. In anotherembodiment, the remote detection of the detectable objects uses a tissueimaging method. Suitable tissue imaging methods include, but are notlimited to: magnetic resonance imaging (MRI); computed tomography (CT);ultrasound imaging; etc. In one example, the orienting fixture 1202 isused to locate and display the saddle trajectory on an image-guidedsurgical (IGS) computer workstation. In another example, the orientingfixture 1202 is used to compute the distance to a target in the brainfrom the orienting fixture. One suitable orienting fixture 1202 is theStealthFighter™, manufactured by Medtronic Inc. of Minneapolis, Minn.

In another example, the flange 1210 of alignment guide 1200 includes analignment window 1214. The alignment window 1214, in one example, is anotch, opening or the like in the flange 1210. The alignment ring 1136includes markings 1216, for instance alpha-numerical markings. Throughcooperative engagement of the keyed teeth 1208 with the grooves 1132(described above) the alignment window 1214 of the alignment guide 1200reveals at least one marking 1216. The keyed teeth 1208, grooves 1132,alignment window 1214, and the markings 1216 are used cooperatively toposition the alignment guide 1200, and thus the orienting fixture 1202,in a desired orientation within the guide lumen 1120. The markings 1216are positioned around the alignment ring 1136 to correspond, in oneexample, to the 45 degree increments between the keyed teeth 1208. Inanother example, an offset alignment guide 1300 (described below)includes an alignment window 1214 similar to that of centered alignmentguide 1200. The alignment window 1214 and markings 1216 allow foraccurate orientation of instrument lumens within an instrument guide(described below).

FIG. 13 is an exploded view of the fixture assembly 102 including thesaddle assembly 1104, alignment ring 1136, an offset alignment guide1300, and an orienting fixture 1202. The offset alignment guide 1300 issimilar to the centered alignment guide 1200 described above, exceptthat its alignment pin 1306 is offset from its central axis. Thealignment pin 1306 is parallel to the central axis of the cylindricalbase 1204 but offset therefrom. When the offset alignment guide 1300 iscoupled to the saddle assembly 1104, the pin 1306 defines a saddletrajectory offset from the center of the guide lumen 1120. Multiplecombinations of saddle trajectories are available with adjustments ofthe alignment ring 1136 and/or the offset alignment guide 1300. In oneexample, the offset alignment guide 1300 is repositioned within thealignment ring 1136 with teeth 1208 at 45 degree increments around the360 degree circle defined by the alignment ring 1136. In anotherexample, the alignment ring 1136 is rotated according to cooperativelyengaged teeth (described above) incrementally spaced every 4 degrees anddisposed within the inner groove of the alignment ring 1136 and lip ofthe saddle slide 1112. In yet another example, the offset alignmentguide 1300 is adjusted according to the teeth 1208 spaced every 45degrees as well as the cooperatively engaged teeth between the alignmentring 1136 and the saddle slide 1112 to achieve additional saddletrajectories.

In another example, the flange 1210 of alignment guide 1300 includes analignment window 1214 as described above regarding alignment guide 1200.The alignment ring 1136 includes markings, for instance alpha-numericalmarkings 1216. The keyed teeth 1208, grooves 1132, alignment window1214, and the markings 1216 are used cooperatively to position thealignment guide 1300 in a desired orientation within the guide lumen1120.

FIG. 14 is a partial sectional and exploded view of the fixture assembly102 including the saddle assembly 1104, alignment ring 1136, and acentered instrument guide 1400. In this example, the centered instrumentguide 1400 includes a first portion 1402 and a second portion 1404. Thesecond portion 1404 is coupled to the saddle assembly 1104 andimmobilized by thumbscrew 1122. Like the alignment guides 1200 and 1300,the centered instrument guide 1400 includes keyed teeth 1406 dimensionedand configured to cooperatively engage the surfaces defining the grooves1132 of the alignment ring 1136. Relative rotation between the centeredinstrument guide 1400 and the saddle assembly 1104 is prohibited by therelationship of the keyed teeth 1406 to the surfaces defining thegrooves 1132 and by the tabs 1138 on the alignment ring 1136 that engagecorresponding teeth 1142 around the guide lumen 1120. In one example, aflange 1408 is disposed substantially between the first portion 1402 andsecond portion 1404. In another example, the flange 1408 is included inthe first portion 1402 or second portion 1404. The flange 1408 extendsfrom and surrounds all or a portion of the centered instrument guide1400. The flange 1408 engages the upper surface of the alignment ring1136 so only the second portion 1404 is within the guide lumen when thecentered instrument guide 1400 is coupled to the saddle assembly 1104.

In this example, a multilumen insert 1412 is disposed within a passage1414 defined by an inner surface of the centered instrument guide 1400.The multilumen insert 1412 is dimensioned and configured to snuglycouple with the inner surface. Instrument lumens 1416 are arranged in apattern within the insert 1412. In this example, a central lumen 1416extends substantially through the insert 1412 along a central axis ofthe insert 1412. Four additional instrument lumens 1416 are disposedaround the central lumen 1416 at 90 degree intervals. In anotherexample, the instrument lumens 1416 are disposed in a differentconfiguration within the insert 1412, for example, in a pentagonalpattern or a three by three matrix of lumens 1416. Each instrument lumen1416 is dimensioned and configured to slidably couple with a guide tube(described below) while constraining lateral movement of the guide tube.In one example, the instrument lumens 1416 are defined by a single innersurface of the multi lumen insert 1412. In other words, the lumens 1416are furrows interconnected within the insert 1412. In another example,the instrument lumens 1416 are separate and distinct lumens extendingthrough the insert 1412.

The first portion 1402 of centered instrument guide 1400 includesproximally accessible keyed teeth 1418. The keyed teeth 1418 aredisposed around the centered instrument guide 1400. In one example, thekeyed teeth 1418 are disposed at 90 degree intervals around the guide1400. In this example, the keyed teeth 1418 and the first portion 1402are dimensioned and configured to couple with the normalizing stageapparatus 100. The keyed teeth 1418 engage with corresponding slots 500(See FIG. 5) on the normalizing stage base 200 to prohibit undesirablerelative rotation between the normalizing stage apparatus 100 and thecentered instrument guide 1400. The offset instrument guide (describedbelow) also includes keyed teeth dimensioned and configured to couplewith the normalizing stage base 200 and prohibit undesirable rotationbetween the normalizing stage apparatus 100 and the offset instrumentguide.

In one example, the instrument guide 1400 includes at least onealignment window 1420 within the flange 1408. The alignment window 1420is sized and shaped to reveal markings 1216 on the alignment ring 1136when the instrument guide 1400 is coupled to the alignment ring 1136. Inone example, the instrument guide 1400 is positioned on the alignmentring 1136 so the alignment window 1420 reveals the same marking 1216determined with the alignment guide 1200. The keyed teeth 1406 aredisposed within the grooves 1132 of the alignment ring 1136 to orientthe instrument guide 1400 on the alignment ring 1136. The instrumentlumens 1416 are oriented in the instrument guide 1400 so matching of themarking 1216 exposed in the alignment window 1214 (alignment guide) tothe marking 1216 exposed in the alignment window 1420 (instrument guide)positions the instrument lumens 1416 in the desired orientation. Theorienting fixture 1202 is used to obtain the desired orientation of theinstrument guide 1400 including the instrument lumens 1416. As a result,if the markings 1216 exposed in the alignment window 1420 are the sameas those in alignment window 1214 the instrument lumens 1416 are in thedesired orientation.

In another example, the instrument guide 1400 includes a skirt 1422. Theskirt 1422 extends downwardly with respect to the flange 1408 and issized and shaped to snugly coupled around the alignment ring 1136.Coupling of the skirt 1422 around the alignment ring 1136 substantiallyprevents rotation of the alignment ring 1132 because the skirt 1422 pinsthe tabs 1138 against the rack 1140. As a result, the tabs 1138 areunable to deform and move around the teeth 1142. The skirt 1422 securesthe instrument guide 1400 in a desired orientation determined, forexample with the markings 1216 and the alignment window 1420 (describedabove).

FIG. 15 is a partial sectional and exploded view of the fixture assembly102 including the saddle assembly 1104, alignment ring 1136, and anoffset instrument guide 1500. The offset instrument guide 1500 issimilar to the centered instrument guide 1400. In this example, theoffset instrument guide 1500 includes a first portion 1502 and a secondportion 1504. In a similar manner to the offset alignment guide 1300,the offset instrument guide 1500 is positionable to define multipletrajectories. The offset instrument guide 1500 is adjusted withpositioning of the guide 1500 within the alignment ring 1136 to engageteeth 1406 with grooves 1132 and positioning of the alignment ring 1136using tabs 1138 and corresponding teeth 1142 on the rack 1140 of thesaddle slide 1112.

FIG. 16A shows an exploded view of the normalizing stage apparatus 100,a guide tube stop 1600, a guide tube 1602, and an obturator 1604. Theguide tube stop 1600 is dimensioned and configured so its cylindricalouter surface fits snugly in the cylindrical inner surface that definesthe guide tube stop lumen 216. In this example, a guide tube stop flange1606 on the guide tube stop 1600 engages an upper lip of a surface thatdefines the lumen 216 of the first stage 210. In one example, guide tubelumens 1608 are arranged in a pattern within the guide tube stop 1600.In this example, a central lumen 1608 extends through the guide tubestop 1600 along a central axis of the guide tube stop 1600. Fouradditional guide tube lumens 1608 are disposed around the central lumen1608 at 90 degree intervals. In another example, the guide tube lumens1608 are disposed in a different configuration through the guide tubestop 1600, for example, in a pentagonal pattern or a three by threematrix of lumens 1608. In yet another example, the guide tube stop 1600includes an outer ring having the flange 1606 and an insert dimensionedand configured to fit therein. The insert includes a pattern of guidetube lumens 1608. Different patterns of lumens 1608 are available indifferent inserts, which may be packaged together (and with any othercomponents such as the normalizing stage) and sold as a kit. Theinstrument lumens 1608 are dimensioned and configured to slidably couplewith the guide tube 1602 while constraining lateral movement of theguide tube 1602. In one example, the guide tube stop lumen 216 is keyedto the guide tube stop 1600. Such keying permits alignment of thepattern of lumens 1608 with the pattern of instrument lumens 1416 of themulti lumen insert 1412.

The guide tube 1602 snugly slides into one of the lumens 1608 of theguide tube stop 1600. In this example, a guide tube flange 1610 issubstantially adjacent a proximal end of the guide tube 1602, andextends partially or completely around the guide tube 1602. The flange1610 engages the upper surface of the guide tube stop 1600 when theguide tube 1602 is plunged through the guide tube stop 1600. Thisprevents the guide tube 1602 from sliding through the guide tube stop1600. In this example, the guide tube 1602 is of a predetermined length,such that a physician or technician could use an “off the shelf” guidetube for a procedure with the normalizing stage with any patient. Theguide tube distal end 1612 is plunged until the flange 1610 engages theguide tube stop 1600, in one example. When the first stage 210 ispositioned at the proper distance to target and the flange 1610 hasengaged the guide tube stop 1600, the distal end 1612 is substantiallyadjacent to the desired target. In one example, the distal end 1612 isthen offset by a desired known distance from the target, for example 15millimeters. In another example, the distal end 1612 is offset from thetarget a smaller increment according to the desires of the physician.

When initially plunging the guide tube 1602 the obturator 1604 isincluded within the guide tube. The obturator 1604 has an outer surfacedimensioned and configured to slidably couple with the inner surface ofthe guide tube 1602. In this example, the obturator 1604 has a lengthsubstantially similar to the guide tube 1602. The distal ends of theobturator 1604 and guide tube 1602 define a blunt distal surface thatprevents coring of the brain or other tissue. Near a proximal end of theobturator 1604 is an obturator flange 1616 that extends partially orcompletely around its circumference. The flange 1616 engages the uppersurface of the guide tube 1602 when the obturator 1604 is within theguide tube. This prevents the obturator 1604 from sliding through theguide tube 1602.

FIG. 16B is an exploded view of one example of a guide tube stop 1620.The guide tube stop 1620 includes an outer ring 1622 sized and shaped soits cylindrical outer surface fits snugly in the cylindrical innersurface that defines the guide tube stop lumen 216 (FIGS. 2 and 16A). Asdescribed above for guide tube stop 1600, the outer ring 1622 of theguide tube stop 1620 includes a flange 1606 radially extending from theouter ring 1622. The flange 1606 engages an upper lip of a surface thatdefines the lumen 216 of the first stage 210. An inner surface 1624 ofthe outer ring 1622 defines at least two grooves 1626 sized and shapedto slidably couple with the guide tube 1602 (FIG. 16B).

The guide tube stop 1620 includes a rocker 1628 sized and shaped to fitwithin the outer ring 1622. The rocker 1628 includes at least twogrooves 1630 sized and shaped to slidably couple with the guide tube1602. The rocker 1628 further includes, in one example a projection 1632extending toward the grooves 1626 of the outer ring 1622. The projection1632 is operable to engage against the inner surface 1624 of the outerring 1622 in one example. In another example, the projection 1632engages against the guide tube 1602 disposed between the rocker 1628 andthe inner surface 1624 to substantially immobilize the guide tube 1602.The rocker 1628 includes, optionally, a stud 1634. The stud 1634, in oneexample, is sized and shaped to extend at least partially through anotch 1636 in the outer ring 1622. The stud 1634 is engaged by athumbscrew 1638 (FIGS. 16A, 16B) that extends through a portion of thefirst stage 210 and into the lumen 216. The thumbscrew 1638 is operableto move the rocker 1628 by engaging the stud 1634. The rocker, in oneexample, moves toward the grooves 1626 of the outer ring 1622 and/orrotates around the stud 1634 so the projection 1632 engages against theouter ring inner surface 1624 or the guide tube 1602.

In another example, the guide tube stop 1620 includes a seat 1640 sizedand shaped to fit between the inner surface 1624 including the grooves1626 and the surface of the rocker 1628 that defines the grooves 1630.In one example, the seat 1640 includes legs 1642 sized and shaped toextend through the outer ring 1622. The legs 1642 include detents 1644substantially adjacent to the free ends of the legs 1642. In anotherexample, detents 1644 engage against the inner surface 1624 of the outerring 1622 during insertion of the legs 1642 into the outer ring 1622.The legs 1642 correspondingly deform and snap into their originalorientations once the detents 1644 exit the outer ring 1622. The detents1644 securely couple the seat 1640 to the outer ring 1622. In anotherexample, the detents 1644 cooperate with an upper surface 1646 of theseat 1640 to securely couple and retain the rocker 1628 and the seat1640 within the outer ring 1622. In yet another example, the detents1644 securely couple the seat 1640 to the outer ring and allowtranslational movement of the seat 1640 within the outer ring 1622.

The legs 1642 of the seat 1640 cooperate with the grooves 1630 of therocker 1628 and the grooves 1626 of the outer ring 1622 to form theguide tube lumens 1608 (FIG. 16A). In one example, the projection 1632of the rocker 1628 cooperates with the inner surface 1624 of the outerring 1622 to define the central guide tube lumen 1608. In anotherexample, the guide tube lumens 1608 are aligned with the pattern 1648extending through the upper surface 1646.

When assembled, the guide tube stop 1620 operates to pass at least oneguide tube 1602 through one of the guide tube lumens 1608. In oneexample, the guide tube lumens 1608 are sized and shaped so the guidetube 1602 is slidably coupled with the guide tube stop 1620. In anotherexample, the guide tube lumens 1608 of the guide tube stop 1620 arealigned with the instrument lumens 1416 in the instrument guides 1400,1500 (FIGS. 14 and 15) using corresponding keys and recesses included onthe first stage 210 and the guide tube stop 1620. In yet anotherexample, the thumbscrew 1638 is turned to clamp the guide tube stoparound the guide tube 1602 and substantially immobilize the guide tube1602 (described below). Immobilizing the guide tube 1602 substantiallyprevents undesirable movement of the guide tube 1602 such as duringexchange of instruments when the instruments are drawn through the guidetube 1602.

In one example, the cooperative relationship of the rocker 1628 with theouter ring 1622 and the seat 1640 facilitates clamping of the guide tube1602 in any of the guide tube lumens 1608. In one example, a guide tube1602 is inserted through the pattern 1648 into the guide tube lumens1608. The thumb screw 1638 is operated to engage the stud 1634 and movethe rocker 1628 toward the grooves 1626 of the outer ring 1622. Wherethe guide tube 1602 is disposed within one of the guide tube lumens 1608between the rocker 1628 and the seat 1640, the rocker 1628 moves untilthe opposing surfaces defining the grooves 1630 and the legs 1642 engageagainst and securely clamp around the guide tube 1602. In anotherexample, the guide tube 1602 is disposed between the projection 1632 andthe inner surface 1624 substantially adjacent to the grooves 1626. Therocker 1628 moves toward the inner surface 1624 and clamps the guidetube 1602 between the projection 1632 and the inner surface 1624. In oneexample, the rocker 1628 pivots around the stud 1634 to engage and clampthe guide tube 1602. In yet another example, the guide tube 1602 isdisposed between the legs 1642 and the grooves 1626. The rocker 1628moves and engages against the seat 1640. The seat 1640 moves with therocker 1628 toward the grooves 1626. The guide tube 1602 is clampedbetween the legs 1642 and the inner surface 1624 defining the grooves1626. The guide tube stop 1620 is thereby operable to clamp andimmobilize the guide tube 1602, including multiple guide tubes 1602, inany of the guide tube lumens 1608.

FIG. 17 is a perspective view of the normalizing stage 100 arranged foradvancing a first instrument 1700, for example a recording electrode. Inthis example, the guide tube stop 1600 is coupled to the first stage210, as described above. The guide tube 1602 extends through the guidetube stop 1600 and the first stage 210. The guide tube flange 1610prevents the guide tube 1602 from sliding completely through the guidetube stop 1600. A spacer tube 1702 is positioned within the guide tube1602 and is dimensioned and configured to slidably couple with the innersurface of the guide tube 1602. The spacer tube 1702 includes a spacertube flange 1704 extending partially or completely about its proximalcircumference. The flange 1704 engages the upper surface of the guidetube 1602 when the spacer tube 1702 is within the guide tube 1602 andprevents the spacer tube from sliding through the guide tube 1602.

The first instrument 1700 is fed through the spacer tube 1702 toward thetarget. The spacer tube 1702 constrains lateral movement of the firstinstrument 1700. Therefore, the first instrument moves along thetrajectory 228 defined by the socket 202 (or parallel to the trajectory228 when using an offset lumen 1608) because the guide tube 1602 andspacer tube 1702 are aligned with that trajectory 228. A portion of thefirst instrument 1700 is immobilized within a retaining assembly 1706that is coupled to the second stage 218 within the retaining assemblyorifice 226. The thumbscrew 232 tightens the retaining assembly aroundthe first instrument 1700. The retaining assembly 1706 immobilizes theportion of the first instrument 1700 with respect to the second stage218. As a result, translation of the second stage 218 correspondinglytranslates the first instrument 1700 within the spacer tube 1702 andguide tube 1602.

FIG. 18 is a front view of a bracket assembly 1800 including a bracket1802, a measurement tube 1804, and a second instrument 1806, for examplea stimulation electrode. In this example, the bracket has a distalcollar base 1808 dimensioned and configured to snugly couple with thesecond stage 218 within the retaining assembly orifice 226. Ameasurement tube lumen extends through the collar base 1808 at thedistal end of the bracket 1802. The measurement tube lumen isdimensioned and configured to couple with a measurement tube 1812. Themeasurement tube 1812 extends from a proximal end 1814 to a distal end1816. The proximal end 1814 is coupled to the bracket 1802 at thebracket proximal end against retaining prongs 1818. In this example,four prongs 1818 extend from each side of the bracket 1802. The innersurfaces of the prongs couple with the proximal end 1814 of themeasurement tube 1812. In another example, additional or fewer prongs1818 are included with the bracket 1802. In yet another example, eachside of the bracket 1802 is dimensioned and configured to couple withthe measurement tube 1812. In this example, the proximal end of thebracket 1802 immobilizes a portion of the second instrument 1806 with athumbscrew 1820 or the like that extends through one side of the bracketinto a furrow 1822 carrying the second instrument. The thumbscrew 1820is rotated until one end engages the second instrument 1806 andimmobilizes the instrument 1806 against the opposing side of the bracket1802.

The measurement tube 1812 is used to calibrate the operating length ofthe second instrument 1806. The second instrument 1806 is positionedwithin the measurement tube 1812 and immobilized by the thumbscrew 1820so a distal end of the second instrument is substantially coterminouswith the distal end 1816 of the measurement tube. The calibration of thesecond instrument 1806 length with respect to the measurement tube 1812allows the distal end of the second instrument to plunge to the targetarea determined with the first instrument (described below).Additionally, the bracket 1802 provides additional instrument length forthe guide tube 1602 to advance along, as described below. Themeasurement tube 1812 eliminates the need for measuring out the secondinstrument 1806 thereby simplifying the determination of the secondinstrument 1806 length.

Operation of the Normalizing Stage Assembly with Centered AlignmentGuides and Centered Instrument Guides

In one example of operation, a burr hole is cut into the skull of thepatient. As shown in FIG. 11, the instrument immobilizer 1100 is coupledto the skull around the burr hole. In an example, the instrumentimmobilizer 1100 is coupled to the skull with bone screws. Then, thesaddle assembly 1104 is coupled to the instrument immobilizer 1100, suchas by screws extending through the base ring 1108. The alignment ring1136 is disposed around the cylindrical wall defining the guide lumen1120. The alignment ring 1136 engages the inward turned lip of thesaddle slide 1112, as described above. As shown in FIG. 12, the centeredalignment guide 1200 is disposed within the guide lumen 1120. Thecentered alignment guide keyed teeth 1208 engage the correspondinggrooves 1132 of the alignment ring 1136. The engagement of the keyedteeth 1208 to the grooves 1132 and the engagement of the alignment ring1136 to the rack 1140 of the saddle slide 1112 prevents unwantedrotation between the centered alignment guide 1200 and the saddleassembly 1104.

The orienting fixture 1202, illustrated in FIG. 12, is coupled to thealignment pin 1206. In this example, the alignment guide thumbscrew 1212immobilizes the orienting fixture 1202 between the thumbscrew and thealignment pin 1206. The saddle assembly 1104 is then adjustedrotationally, arcuately, or both to define a trajectory to a desiredtarget of the brain. The orientation fixture 1202 is used to display thetrajectory on an IGS workstation during the adjustment. Once the desiredtrajectory is obtained thumbscrews 1114 are tightened on the saddleassembly 1104 to prevent further rotational and arcuate motion of thesaddle assembly 1104. The alignment guide 1200 and alignment ring 1136are rotated around guide lumen 1120. In one example, the tabs 1138 andteeth 1142 of the rack 1140 cooperatively engage for rotation of thealignment guide 1200 and the alignment ring 1136 at clicking increments(e.g. 4 degree increments). A marking 1216 is revealed through thealignment window 1214. The alignment guide 1200 and alignment ring 1136are rotated so the marking 1216 and thereby the alignment guide 1200coupled to the alignment ring 1136 are in a desired orientation (e.g.,an anterior-to-posterior orientation of a skull). As a result, thepattern of instrument lumens 1416 (See FIG. 14) will be in the samedesired orientation when the instrument guide 1400 is coupled to thealignment ring 1136 (described below).

Alignment of the alignment guide 1200 and the alignment ring 1136 to thedesired orientation is done visually in one example. In another example,an IGS workstation is used to measure rotation of the alignment guide1200 and the alignment ring 1136 and to determine when the desiredorientation is achieved. The orienting fixture 1202 is keyed to thealignment guide 1200 in this example, to align the orienting fixture1202 with respect to the alignment guide 1200.

The relative location of the orienting fixture 1202 is also used by theIGS workstation to determine the proper location of the first stage 210with respect to the desired target area, and proper lengths ofinstruments 1700, 1806, and the guide tube 1602, obturator 1604 andspacer tube 1702. In one example, the IGS workstation determines theinitial position of the first stage 210 with respect to the target area.The first stage 210 is moved with respect to the base 200 and theposition of the first stage 210 relative to the target area isdetermined with, for instance, the scale 304 and reference mark 306(described below)

FIG. 19 is a perspective view illustrating the fixture assembly 102,normalizing stage assembly 100, and a first instrument 1700. Theorienting fixture 1202 and the centered alignment guide 1200 have beenremoved from the saddle assembly 1104. The centered instrument guide1400 is then coupled to the saddle assembly 1104 in a similar manner tothe centered alignment guide 1200. The centered instrument guide 1400 iscoupled to the alignment ring 1136 so the same marking 1216 used toposition the alignment guide 1200 and the alignment ring 1136 isrevealed in the alignment window 1420. The centered instrument guide1400 is thereby positioned in the desired orientation determined withthe alignment guide 1200 and the orientation fixture 1202 (describedabove). Revealing the same marking 1216 ensures proper positioning ofthe instrument guide 1400 and the corresponding instrument lumens 1416to the desired orientation.

The first stage actuator 300 (FIG. 3) is turned to initially adjust thefirst stage 210 to substantially coincide with the desired distance asdetermined with the orienting fixture 1202. The scale 304 and referencemark 306 are used to measure the position of the first stage 210 withrespect to the desired target area. If necessary, the second stage 218is adjusted with the actuator knob 308 to a desired starting position.In one example, the starting position for the second stage 218 is readfrom the scales 316A-C, attached to the first stage 210, and a referencemarking 314, attached to a protrusion 310 extending from the secondstage 218. In another example, the position of the second stage 218 isdetermined with the potentiometer assembly 600.

In one example, the stages 210, 218 are adjusted before coupling thenormalizing stage apparatus 100 to the centered instrument guide 1400.In another example, the adjustments are made after coupling thenormalizing stage 100 to the centered instrument guide 1400. Keyed teeth1418 on the centered instrument guide 1400 engage with correspondingslots 500 within the socket 202 of the base 200. The keyed teeth 1418and slots 500 prevent relative rotation between the centered instrumentguide 1400 and the normalizing stage assembly 100. Thumbscrew 204 istightened to securely couple the normalizing stage 100 to the centeredinstrument guide 1400.

In FIG. 16A, the guide tube 1602 and obturator 1604 are coupled to eachother, so the obturator is disposed within the guide tube 1602 and theobturator flange 1616 engages the upper surface of the guide tube. Theguide tube distal end 1612 and obturator distal end 1614 define a bluntsurface. Both the guide tube 1602 and obturator 1604 are of a standardlength that is factored into the function used to determine the positionof the first stage 210 with the orienting fixture 1202 (FIG. 12). Theguide tube 1602 and obturator 1604 are plunged through a guide tubelumen 1608 within the guide tube stop 1600. The guide tube flange 1610engages the guide tube stop 1600 to prevent unwanted advancement of theguide tube 1602 beyond the guide tube stop 1600. The guide tube 1602 andobturator 1604 also extend through the centered instrument guide 1400,specifically, one of the instrument guide lumens 1416. In this example,because the first stage 210 is adjusted to substantially coincide withthe distance measurement described above, the distal ends of thestandard length guide tube 1602 and obturator 1604, are substantiallyadjacent to the desired target when plunged. In one example, thesedistal ends are offset a desired approach distance from the target, forexample, 15 millimeters. In another example, the physician offsets thedistal ends a desired approach distance.

After plunging of the guide tube 1602 and obturator 1604, the obturator1604 is removed from the guide tube 1602, such as by grasping theobturator flange 1616 by hand or with a tool such as a forceps to liftthe obturator 1604 out of the guide tube 1602.

After removal of the obturator 1604, the spacer tube 1702 (FIG. 17) isthen inserted into the guide tube 1602 until the spacer tube flange 1704engages the upper surface of the guide tube 1602. The spacer tube 1702has a length substantially similar to that of the guide tube 1602. As aresult, the distal end of the spacer tube 1702 is substantially adjacentto the distal end of the guide tube 1602.

As shown in FIG. 17, the retaining assembly 1706 is then inserted intothe retaining assembly lumen 226 of the second stage 218. The firstinstrument 1700 is fed through the retaining assembly 1706 and intospacer tube 1702. In this example, the thumbscrew 232 is rotated totighten the retaining assembly 1706 around the first instrument 1700.The first instrument 1700 is of a standard predetermined length, forsuch an off the shelf instrument 1700. In one example, the firstinstrument 1700 is a recording electrode with a flange 1708 at itsproximal end to engage an upper surface of the retaining assembly 1706.The distance between a distal end of the instrument and the flange is astandard predetermined length. The first stage 210 and second stage 218are initially positioned to take into account the distance to thedesired target and the predetermined lengths of the instruments andtubes (described above). As a result, the distal end of the standardlength first instrument 1700, when plunged with the flange 1708 engagedto the retaining assembly 1706, is substantially adjacent to the distalend of the guide tube 1602 and the distal end of the spacer tube 1702.The distal end of the first instrument 1700 and the distal end of theguide tube 1602 are substantially adjacent to the desired target or areoffset from the desired target area some distance, for example, 15millimeters, as described above.

In this example, a physician or technician then operates actuator knob308 to move the second stage 218 and first instrument 1700 coupledthereto along the screw 220. The distal end of the first instrument 1700is moved toward, away or through the desired target, as desired. In oneexample, the relative position of the distal end of the first instrument1700 with respect to the desired target area is read from the scale 316Awith reference marking 314. In another example, the relative position ofthe first instrument 1700 is read from the reference marking 402 againstthe fine scale 400 (FIG. 4) coupled to the screw 220. In still anotherexample, the relative position of the first instrument 1700 is measuredwith a potentiometer assembly 600, as described above. In anotherembodiment the hydraulic system 700 is used to move the second stage 218through actuation of the master piston 708 with respect to the mastercylinder 706.

If the physician is satisfied with the track of the first instrument1700 to the desired target, a second instrument 1806 is substituted(described below). If the physician is not satisfied with the track ofthe first instrument 1700 (for example, a blood vessel blocksadvancement of the first instrument 1700) it is retracted away from thetarget. The retaining assembly 1706 is loosened through thumbscrew 232,and the first instrument 1700 is removed from the normalizing stageassembly 100. The retaining assembly 1706 is then removed from thesecond stage 218. The guide tube 1602 and spacer tube 1702 are thenremoved from the guide tube stop 1600. The physician may then plungeanother guide tube 1602 and obturator 1604 in an adjacent guide tubelumen 1608. The process described above is then substantially repeatedfor the new track created by the guide tube 1602 in the adjacent lumen1608.

Operation of the Normalizing Stage Assembly with Offset Alignment Guidesand Offset Instrument Guides

Alternatively, the physician removes the entire normalizing stageassembly 100, and the centered instrument guide 1400. An offsetalignment guide 1300 (FIG. 13) is coupled to the saddle assembly 1104.In another example, the physician uses the offset alignment guide 1300from the beginning instead of the centered alignment guide 1200, if sodesired. The keyed teeth 1214 of the offset alignment guide 1300 and thecorresponding grooves 1132 on the alignment ring 1136 make the offsetguide 1300 positionable at 45 degree increments (FIG. 11). Additionally,the offset alignment guide 1300 is positionable at 4 degree incrementsthrough actuation of alignment ring 1136 around the rack 1140. Theorienting fixture 1202, illustrated in FIG. 12, is coupled to thealignment pin 1306. In this example, the alignment guide thumbscrew 1212immobilizes the orienting fixture 1202 between the thumbscrew and thealignment pin 1306.

The saddle assembly 1104 is then adjusted rotationally and/or arcuately,to define a trajectory to a desired target of the brain. Once thephysician is initially satisfied with the trajectory of the saddleassembly 1104 and offset alignment guide 1300 coupled thereto,thumbscrews 1114 are tightened on the saddle assembly 1104 to preventfurther rotational and arcuate motion of the saddle 1104. The locationof the orienting fixture 1202 with respect to the desired target isdetected through the imaging methods described above. The relativelocation of the orienting fixture 1202 is used to determine the desiredlocation of the first stage 210 with respect to the target. An IGS workstation, for example, takes into account the lengths of standardized“off the shelf” instruments 1700, 1806, and the guide tube 1602,obturator 1604 and spacer tube 1702.

The alignment guide 1300 and alignment ring 1136 are rotated aroundguide lumen 1120 as described above with the alignment guide 1200. Amarking 1216 is revealed through the alignment window 1214. Thealignment guide 1300 and alignment ring 1136 are rotated so the marking1216 and thereby the alignment guide 1300 coupled to the alignment ring1136 are in a desired orientation (e.g., an anterior-to-posteriororientation of a skull). As a result, the pattern of instrument lumens1416 (See FIG. 15) will be in the same desired orientation when theinstrument guide 1500 is coupled to the alignment ring 1136 (describedbelow). Aligning of the alignment guide 1300 and the alignment ring 1136to the desired orientation is done, for instance, visually or with anIGS workstation as described above for alignment guide 1200.

The orienting fixture 1202 and the offset alignment guide 1300 areremoved from the saddle assembly 1104. The offset instrument guide 1500is coupled to the saddle assembly 1104 in the same orientation as wasthe offset alignment guide 1300. In one example, the offset instrumentguide 1500 is coupled to the alignment ring 1136 so the same marking1216 used to position the alignment guide 1300 and the alignment ring1136 is revealed in the alignment window 1420. The offset instrumentguide 1500 is thereby positioned in the desired orientation determinedwith the alignment guide 1300 and the orientation fixture 1202(described above). Revealing the same marking 1216 ensures properpositioning of the instrument guide 1500 and the correspondinginstrument lumens 1416 to the desired orientation.

The first stage actuator 300 is turned to initially adjust the firststage 210 to substantially coincide with the distance determined withthe orienting fixture 1202. The scale 304 and reference mark 306 areused to measure the position of the first stage 210 with respect to thedesired target. If necessary, the second stage 218 is adjusted with theactuator knob 308 to a desired starting position. In one example, thestarting position for the second stage 218 is read from one of thescales 316A-C, attached to the first stage 210, and a reference marking314, attached to a protrusion 310 extending from the second stage 218.In another example, the position of the second stage 218 is determinedwith the potentiometer assembly 600 (FIG. 6) coupled between the secondstage 218 and the first stage 210.

The normalizing stage apparatus 100 is coupled to the offset instrumentguide 1500 (See FIG. 15). In this example, the adjustments to the stages210, 218 are performed before coupling the normalizing stage apparatus100 to the offset instrument guide 1500. In another example, theadjustments are made after coupling the normalizing stage 100 to theoffset guide 1500. Keyed teeth 1510 on the offset guide 1500 engage withcorresponding slots 500 within the socket 202 of the base 200. Thisprevents relative rotation between the offset instrument guide 1500 andthe normalizing stage assembly 100. Thumbscrew 204 is tightened tosecurely couple the normalizing stage 100 to the offset instrument guide1500.

The obturator 1604 is inserted into the guide tube 1602 until theobturator flange 1616 engages the upper surface of the guide tube 1602.The guide tube distal end and obturator distal end define a bluntsurface. Both the guide tube 1602 and obturator 1604 are of a standardlength that is factored into the function used to determine the positionof the first stage 210 with the orienting fixture 1202. The guide tube1602 and obturator 1604 are plunged together through a guide tube lumen1608 within the guide tube stop 1600 until the guide tube flange 1610engages the guide tube stop 1600. The guide tube 1602 and obturator 1604also extend through the offset instrument guide 1500, specifically, oneof the instrument guide lumens 1416. In this example, because the firststage 210 is adjusted to substantially coincide with the distancemeasurement described above, the distal ends of the standard lengthguide tube 1602 and obturator 1604, are substantially adjacent to thedesired target area when plunged. In one example, the distal ends areoffset from the target a desired approach distance, for example, 15millimeters. In another example, the physician offsets the distal ends adesired approach distance from the target.

After plunging of the guide tube 1602 and obturator 1604, the obturator1604 is removed from the guide tube 1602. The spacer tube 1702 isinserted into the plunged guide tube 1602 until the spacer tube flange1704 engages the upper surface of the guide tube 1602. The spacer tube1702 has a length substantially similar to that of the guide tube 1602so the distal end of the spacer tube 1702, when inserted, issubstantially adjacent to the distal end 1612 of the guide tube 1602.

FIG. 19 is a perspective view of the normalizing stage apparatus 100showing the relation of the first instrument 1700 to the normalizingstage apparatus 100. Operation of the normalizing stage apparatus 100with the illustrated centered instrument guide 1400 is substantiallysimilar to operation with the offset instrument guide 1500. Theretaining assembly 1706 is coupled to the second stage 218 and withinretaining assembly orifice 226 after removal of the obturator 1604. Thefirst instrument 1700 is then fed through the retaining assembly 1706 inthe second stage 218 and into spacer tube 1702. In this example, thethumbscrew 232 is rotated to tighten the retaining assembly 1706 aroundthe first instrument 1700. The first instrument 1700 is of a standardlength. In one example, the first instrument 1700 is a recordingelectrode. In this example, the recording electrode has a distal end,and a flange 1708 disposed at its proximal end to engage an uppersurface of the retaining assembly 1706. The distance between the distalend of the instrument 1700 and the flange 1708 is a standard length. Thefirst stage 210 and second stage 218 are initially positioned withrespect to the desired target. The positioning of the first stage 210and second stage 218 takes into account the lengths of the standardized(off the shelf) instruments and tubes (described above). As a result,the distal end of the standard length first instrument 1700, whenplunged with the flange 1708 engaged to the retaining assembly 1706, issubstantially adjacent to the distal end 1612 of the guide tube 1602 andthe distal end of the spacer tube 1702. In one example, the distal endof the first instrument 1700 and the distal end of the guide tube 1602are substantially adjacent to the desired target. In another example,the distal end 1612 and distal end of the first instrument 1700 areoffset from the desired target some distance, for example, 15millimeters, as described above.

In this example, a physician or technician then turns actuator knob 308to move the second stage 218, and first instrument 1700 coupled thereto,along the screw 220. The distal end of the first instrument 1700 ismoved toward, away or through the desired target area as desired. In oneexample, the relative position of the distal end of the first instrument1700 with respect to the desired target is read from the scale 316A withreference marking 314. In another example, the relative position of thefirst instrument 1700 distal end is read on the scale 316 with respectto the distal end of the guide tube 1602. In yet another example, therelative position of the first instrument 1700 is read from thereference marking 402 against the fine scale 400 (FIG. 4) coupled to thescrew 220. In still another example, the relative position of the firstinstrument 1700 is measured with a potentiometer assembly 600, asdescribed above. In another embodiment the hydraulic system 700 is usedto move the second stage 218 through actuation of the master piston 708with respect to the master cylinder 706.

If the physician is satisfied with the track of the first instrument1700 to the desired target, a second instrument 1806 is substituted(described below). If the physician is not satisfied with the track ofthe first instrument 1700 (for example, a blood vessel blocksadvancement of the first instrument 1700) it is retracted away from thetarget. The retaining assembly 1706 is loosened through thumbscrew 232,and the first instrument is removed from the normalizing stage assembly100. The retaining assembly 1706 is then removed from the second stage218. The guide tube 1602 and spacer tube 1702 are then removed from theguide tube stop 1600. The physician may then plunge another guide tube1602 and obturator 1604 in an adjacent guide tube lumen 1608. Theprocess described above is then substantially repeated for the new trackcreated by the guide tube 1602 in the adjacent lumen 1608. In anotherexample, the physician adjusts the position of the offset instrumentguide 1500 through actuation of the alignment ring 1136. In one example,adjustment of the guide 1500 position also requires use of the offsetalignment guide 1300 to redetermine the relative position of the firststage 210 with respect to the target area and standardized instrumentsand tubes. In still another example, the physician removes the offsetinstrument guide 1500 and uses a centered alignment guide 1200 andcentered instrument guide 1400 to make another track to the desiredtarget area.

Operation of the Normalizing Stage Assembly with the Second Instrument

FIG. 20 is a perspective view showing the normalizing stage apparatus100, bracket assembly 1800, and the second instrument 1806. Beforecoupling of the bracket 1802 to the normalizing stage apparatus, thebracket assembly 1800 is used to measure out the length for the secondinstrument 1806. The measurement tube 1804 (FIG. 18) is coupled to thebracket 1802 so the tube is disposed within the measurement tube lumen1810 and the proximal end 1814 of the tube is coupled to the bracket bythe retaining prongs 1818. The second instrument 1806 is fed into themeasurement tube 1804 until the distal end of the second instrument issubstantially coterminous with the distal end 1816 of the measurementtube (FIG. 18). A portion of the second instrument 1806 is immobilizedby thumbscrew 1820 that engages the second instrument 1806 against theopposing side of the bracket 1802. The measurement tube is thenuncoupled from the bracket 1802. The retaining assembly 1706 isuncoupled from the second stage 218, and the spacer tube 1702 is removedfrom engagement with the guide tube 1602 in a similar manner as theobturator 1604. The bracket 1802 is coupled to the second stage withinthe retaining assembly orifice 226. In this example, the retainingassembly orifice 226 includes a slot and the bracket collar base 1808includes a key dimensioned and configured to cooperatively engage thesurface defining the slot. The thumbscrew 232 is tightened to securelycouple the bracket 1802 to the second stage. The slot and keyrelationship determines the orientation of the bracket 1802 relative tothe second stage 218. The second instrument 1806 is then fed, distal endfirst, through the guide tube 1602 and plunged toward the target alongthe track determined with the first instrument 1700.

The bracket 1802 provides a constant offset distance between the secondstage 218 and the bracket proximal end where the second instrument 1806is coupled. This constant offset distance is reflected in the additionallength of the second instrument 1806 over the first instrument 1700. Theconstant offset allows the distal end of the second instrument 1806 toplunge to the location determined with the first instrument 1700. Inother words, when plunging the second instrument 1806, the normalizingstage apparatus 100, specifically first stage 210 and second stage 218,are in the positions determined with the first instrument 1700. Thesecond instrument 1806 thus plunges so the distal end of the instrumentis substantially adjacent to the prior location of the first instrument1700 distal end.

A perspective view of the normalizing stage apparatus 100, the secondinstrument 1806, the guide tube 1602, and the instrument immobilizer1100 is shown in FIGS. 21 and 22. The second instrument 1806 is disposedwithin the guide tube 1602. To remove the guide tube 1602 and leave thesecond instrument 1806 at the desired location, the guide tube 1602 ismoved out of engagement with the guide tube stop 1600. The guide tube1602 is advanced along the second instrument 1806 which is slidablycoupled thereto. As shown in FIG. 21, the guide tube 1602 is moved atleast until the distal end of the guide tube is above the instrumentimmobilizer 1100. The retaining piece 1106 is then moved into engagementagainst the second instrument 1806 to immobilize the instrument betweenthe retaining piece and the opposing surface of the instrumentimmobilizer 1100, as shown in FIG. 22. The second instrument 1806 issubstantially immobilized between the instrument immobilizer 1100 andthe distal end of the second instrument 1806. Additionally, the distalend of the second instrument 1806 is located at the desired targetlocation along the track determined with the first instrument 1700.

The thumbscrew 1820 is loosened to release the second instrument 1806from engagement to the bracket 1802. In this example, the thumbscrew 204is loosened to allow uncoupling of the normalizing stage assembly 100from the instrument guide (1600 or 1500). The saddle assembly 1104 isuncoupled from the instrument immobilizer 1100 by loosening screwsextending therebetween, in one example. In another example, the saddleassembly 1104 is uncoupled from the instrument immobilizer 1100 whilethe normalizing stage assembly 100 is still coupled to the saddleassembly 1104. In yet another example, the second instrument 1806 ispulled through an orifice between the saddle slide 1112 and the towerbase 1110 to uncouple the second instrument from the normalizing stageassembly 100. The saddle assembly 1104 and normalizing stage assembly100 are then easily uncoupled from the instrument immobilizer 1100 andthe second instrument 1806 is not otherwise disturbed. The secondinstrument 1806 is left engaged to the instrument immobilizer with thedistal end at the desired target.

FIG. 23 is a perspective view showing the instrument immobilizer 1100,the second instrument 1806, and a cap 2300. The portion of the secondinstrument 1806 outside of the skull and beyond the instrumentimmobilizer 1100 is bent over, and the cap 2300 is engaged to theinstrument immobilizer. In this example, the cap is elastic and deformsto snugly engage with the instrument immobilizer 1100 and retain thesecond instrument 1806 in its orientation.

Techniques for Using a Normalizing Stage Apparatus

FIG. 24 is a block diagram illustrating generally, by way of example,but not by way of limitation, examples of certain techniques for using anormalizing stage, such as the normalizing stage apparatus 100 ofFIG. 1. The normalizing stage, in this example, includes a base, a firststage moveably coupled to the base and operable to move with respect tothe base, and a second stage moveably coupled to the first stage andoperable to move with respect to the first stage and the base. Thetechniques disclosed herein need not be carried out in the exact orderillustrated in the block diagrams of FIGS. 24-29. At 2402, a fixingassembly is coupled to the body. In this example, the fixing assembly iscoupled to the skull. At 2404, the relative position of the normalizingstage with respect to a desired target, the instruments, and otherequipment (described above) is determined. A first instrument is plungedand advanced to the target at 2406. In this example, the firstinstrument is a recording electrode. At 2408, a second instrument isplunged to the target area. In this example, the second instrument is astimulation electrode. At 2410, the second instrument is immobilized andthe normalizing stage and fixing assembly are removed.

FIG. 25 is a more detailed block diagram illustrating techniques forcoupling the fixing assembly to the skull 2402. At 2500, an instrumentimmobilizer is coupled to the skull. In this example, the instrumentimmobilizer is coupled around a burr hole in the skull. A saddle iscoupled to the instrument immobilizer at 2502. In this example, thesaddle is aligned with a trajectory defined by the instrumentimmobilizer. At 2504, an alignment ring, such as the alignment ring 1136in FIG. 11, is coupled to the saddle.

FIG. 26 is a more detailed block diagram illustrating techniques fordetermining the relative position of the normalizing stage with respectto the desired target area, the instruments, and other equipment 2404.At 2600, an alignment guide is coupled to the saddle and engaged to thealignment ring. In one example, the alignment guide is an embodimentsuch as centered alignment guide 1200. The alignment guide includes analignment pin aligned with the longitudinal axis of the alignment guide.In another example, the alignment guide includes an alignment pinparallel to, and offset from, the longitudinal axis of the alignmentguide. At 2602, an orienting fixture, such as orienting fixture 1202, iscoupled to the alignment guide. In one example, the orienting fixture iscoupled to the alignment pin of the alignment guide. At 2604, the saddleand the alignment ring are adjusted to determine a trajectory andorientation to the desired target. In this example, the saddle isadjusted rotationally and/or arcuately. The location of a first stage ofthe normalizing stage is determined with respect to the desired target,standardized (off the shelf) instruments, and tubes used to plunge theinstruments, at 2606. In this example, the location of the first stageis determined with imaging of the orienting fixture. At 2608, theorienting fixture and alignment guide are uncoupled and removed.

FIG. 27 is a more detailed block diagram illustrating techniques forplunging the first instrument and advancing it toward the target area2406. At 2700, the first stage is positioned to the desired startingposition determined in 2404 (described above). At 2702, the second stageis positioned to a desired starting position. In one example, the secondstage is not adjusted because it is already calibrated to a startingposition and is moveably coupled to the first stage. In this example,the second stage moves correspondingly with the first stage as the firststage is moved. At 2704, an instrument guide is coupled to the saddleand engages with the alignment ring. In one example, the instrumentguide has at least one instrument guide lumen aligned with thelongitudinal axis of the instrument guide, as described with centeredinstrument guide 1400 above. In another example, the instrument guideincludes at least one instrument guide lumen parallel to, and offsetfrom, the longitudinal axis of the instrument guide. In yet anotherexample, the offset instrument guide lumen has substantially the samealignment as the alignment pin of the offset alignment guide (describedabove). At 2706, the normalizing stage is coupled to the instrumentguide. In this example, the normalizing stage has a base that defines atrajectory, and the trajectory is parallel to the longitudinal axis ofthe instrument guide. In another example, the trajectory of thenormalizing base is aligned with the longitudinal axis of the instrumentguide. At 2708, a standard length (usable off the shelf) guide tube andstandard length (also usable off the shelf) obturator are plungedtogether through a guide tube stop coupled to the first stage of thenormalizing stage until engaged to the guide tube stop. In this example,the obturator is coupled with the guide tube so the distal ends of theguide tube and obturator define a blunt surface. The obturator isremoved from engagement with the guide tube at 2710. At 2712, a standardlength off the shelf spacer tube is plunged through the guide tube stop,specifically the guide tube, until engaged with the guide tube. In thisexample, the guide tube, obturator, and spacer tube include flanges thatengage surfaces, for example the guide tube stop, and prevent furtherplunging of the guide tube, obturator and/or spacer tube. At 2714, thefirst instrument is plunged through a retaining assembly coupled to thesecond stage and the spacer tube toward the target. Because of thepositioning of the first stage 2700 (and second stage 2702 ifnecessary), the first instrument distal end is coterminous with thedistal end of the guide tube when plunged. At 2716, the first instrumentis moved toward, away and/or through the desired target. In thisexample, the first instrument is moved outside of the guide tube andtoward the target area.

FIG. 28 is a more detailed block diagram illustrating techniques forplunging the second instrument 2408. At 2800, the first instrument isuncoupled and removed from the second stage retaining assembly and thespacer tube. At 2802, the spacer tube is removed from engagement withthe guide tube. In this example, the spacer tube is removed from theguide tube. At 2804, a length of the second electrode is measured with abracket (for example, bracket 1802) and measurement tube (e.g.measurement tube 1804) coupled to the bracket. In this example, thesecond instrument is fed through the measurement tube and the portion ofthe bracket coupled to the measurement tube. The second instrument iscoupled to the bracket and the measurement tube is uncoupled from thebracket at 2806. At 2808, the bracket is coupled to the second stage ofthe normalizing stage. In this example, the retaining assembly isuncoupled from the second stage and the bracket coupled in its place. At2810, the second instrument is plunged through the guide tube toward thetarget along the track determined with the first instrument.

FIG. 29 is a more detailed block diagram illustrating techniques forimmobilizing the second instrument and removing the stage and fixingassembly 2410. At 2900, the guide tube is moved out of engagement withthe guide tube stop. In this example, the guide tube is advanced upwardrelative to the second stage along the second instrument. At 2902, theinstrument immobilizer (for example, instrument immobilizer 1100) isactuated to immobilize a portion of the second instrument from theinstrument immobilizer to the distal end of the second instrument at thetarget. In one example, the instrument immobilizer includes a retainingpiece 1106 (FIG. 11) that is actuated to engage the second instrumentand immobilize it against the instrument immobilizer. At 2904, thesecond instrument is uncoupled from the bracket. In one example, thebracket is uncoupled and removed from the second stage. The normalizingstage is removed from the instrument guide at 2906. At 2908, the saddleis uncoupled and removed from the instrument immobilizer. In anotherexample, the normalizing stage is left coupled to the instrument guideand the saddle, and the saddle, instrument guide, and normalizing stageare uncoupled as a single unit from the instrument immobilizer. At 2910,the non-immobilized portion of the second instrument is bent over and acap is engaged to the instrument immobilizer to further retain thesecond instrument.

CONCLUSION

The various embodiments of the normalizing stage in this document arepresented as illustrative examples, and are not intended to be limiting.The normalizing stage embodiments discussed in this document will becapable of use with a variety of fixture assemblies, including thefixture assemblies discussed above. Additionally, the normalizing stageand the techniques discussed herein are not limited to advancinginstruments toward, away or through target locations within a subject'sbrain. The normalizing stage apparatus and techniques are alsoapplicable to targeting other locations within a subject. Furthermore,the normalizing stage and techniques discussed in this document may alsobe useful for moving instruments toward, away or through desired targetlocations within any material.

The normalizing stage described in this document provides a standarddistance to a desired target. The standard distance provided with thefirst stage allows use of standard length, off the shelf, instruments,guide tubes, spacer tubes and obturators. The second stage movescorrespondingly with the first stage. Therefore, positioning of thefirst stage a standard distance from the desired target likewisepositions the second stage with respect to the desired target area. Oncethe first stage is positioned the standard distance from the target, thesecond stage, moveably coupled to the first stage, moves the standardinstrument toward, away and through the target location as desired. Inother words, the first stage allows use of off the shelf instruments,tubes and the like, while the second stage moves the off the shelfinstruments toward and/or away from the target. Thus the normalizingstage expedites the introduction of instruments to the target location.Additionally, the normalizing stage and the methods for using the sameeliminate time-consuming calculations for physicians and/or technicians,for instance, calculations of the instrument, tube and obturatorlengths. Moreover, the normalizing stage reduces errors by simplifyingthe introduction of instruments with standard length instruments, tubesand the like. Error is reduced by removing calculations of instrumentlengths and the like from the procedure of use.

Moreover, the normalizing stage is a cost effective disposable unit thatcan be used for a procedure and disposed afterwards. The normalizingstage and other equipment described in this document are packagedsterile and used at the point of use. Sterile saline is readilyavailable at most hospitals and clinics and is used prior to theprocedure to fill the hydraulic examples described above.

It is to be understood that the above description is intended to beillustrative, and not restrictive. For example, the above describedembodiments may be used in combination with each other. Many otherembodiments will be apparent to those of skill in the art upon readingand understanding the above description. The scope of the inventionshould, therefore, be determined with reference to the appended claims,along with the full scope of equivalents to which such claims areentitled. In the appended claims, the terms “including” and “in which”are used as the plain-English equivalents of the respective terms“comprising” and “wherein.” Moreover, in the following claims, the terms“first,” “second,” and “third,” etc. are used merely as labels, and arenot intended to impose numerical requirements on the objects.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the invention. Individual elements or features ofa particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the invention, and all such modificationsare intended to be included within the scope of the invention.

1. An apparatus for advancing an instrument into a body comprising: abase, wherein the base defines a trajectory; a first stage moveablycoupled to the base, wherein the first stage is moveable along thetrajectory; a second stage moveably coupled to the first stage, whereinthe second stage is moveable relative to the first stage on or parallelto the trajectory and operable to move an instrument coupled theretowith respect to the base and the first stage; and a hydraulic systemincluding: a hydraulic cylinder coupled to the first stage; a hydraulicpiston coupled to the second stage; and a hydraulic actuator in fluidcommunication with the hydraulic cylinder and hydraulic piston, whereinthe hydraulic actuator is operable to advance the hydraulic piston withrespect to the hydraulic cylinder.
 2. The apparatus of claim 1, whereinthe hydraulic actuator includes a master cylinder coupled to a masterpiston, and the master piston is actuated by a screw coupled between themaster piston and master cylinder.
 3. The apparatus of claim 1, furthercomprising a fluid inlet operable to receive hydraulic fluid, whereinthe fluid inlet includes a check valve.
 4. The apparatus of claim 1,further comprising a liquid impermeable vent coupled to the hydrauliccylinder, wherein the liquid impermeable vent is gas permeable.
 5. Theapparatus of claim 1, further comprising a spring coupled between thefirst stage and the second stage, wherein the spring operates to pull orpush the hydraulic piston toward one end of the hydraulic cylinder andto maintain pressurization in the hydraulic system.
 6. The apparatus ofclaim 1, further comprising a potentiometer coupled between the firststage and the second stage, wherein the potentiometer is operable tomeasure the movement of the second stage relative to the first stage. 7.The apparatus of claim 1, wherein a bearing is coupled between the firststage and the second stage.
 8. An apparatus for advancing an instrumentinto a body comprising: a first stage; a second stage moveably coupledto the first stage, wherein the second stage is moveable relative to thefirst stage on or parallel to a trajectory extending through the firstand second stage; a hydraulic cylinder coupled to the first stage; ahydraulic piston coupled to the second stage; and a hydraulic actuatorin fluid communication with the hydraulic cylinder and hydraulic piston,the hydraulic actuator including a master hydraulic cylinder and amaster hydraulic piston, wherein the hydraulic actuator is operable tomove the second stage relative to the first stage.
 9. The apparatus ofclaim 8, wherein the hydraulic piston is separated from the hydrauliccylinder.
 10. The apparatus of claim 8, further comprising apotentiometer coupled between the first stage and the second stage,wherein the potentiometer is operable to measure the movement of thesecond stage relative to the first stage.
 11. The apparatus of claim 8,wherein the hydraulic cylinder, hydraulic piston and the hydraulicactuator are sized and shaped for filling immediately prior to use. 12.The apparatus of claim 8, further comprising a fluid inlet in fluidcommunication with the hydraulic cylinder, hydraulic piston and thehydraulic actuator, wherein the fluid inlet is sized and shaped toreceive hydraulic fluid.
 13. The apparatus of claim 8, furthercomprising a gas permeable vent coupled to the hydraulic cylinder,wherein the gas permeable vent is liquid impermeable.
 14. The apparatusof claim 8, further comprising a spring coupled between the first stageand the second stage, wherein the spring operates to pull or push thehydraulic piston toward one end of the hydraulic cylinder and tomaintain pressurization in the hydraulic system.
 15. The apparatus ofclaim 8, wherein the hydraulic actuator includes a liquid impermeablemembrane extending between the master hydraulic cylinder and the masterhydraulic piston.
 16. The apparatus of claim 8, wherein a bearing iscoupled between the first stage and the second stage.
 17. The apparatusof claim 8, wherein a roller or linear ball bearing is coupled betweenthe first stage and the second stage
 18. An apparatus for advancing aninstrument into a body comprising: a base defining a trajectory; a firststage moveably coupled to the base and along the trajectory; a secondstage moveably coupled to the first stage and operable to move aninstrument with respect to the base and the first stage; a hydrauliccylinder and a hydraulic piston coupled relative to the first stage andthe second stage; a hydraulic actuator in fluid communication with thehydraulic cylinder and hydraulic piston, wherein the hydraulic actuatoris operable to move the second stage relative to the first stage; aspring coupled between the first stage and second stage, the springoperable to maintain pressurization in the hydraulic cylinder; and abearing coupled between the first stage and the second stage.
 19. Theapparatus of claim 18, wherein the hydraulic actuator includes a masterhydraulic cylinder and a master hydraulic piston and a liquidimpermeable membrane extending between the master hydraulic cylinder andthe master hydraulic piston.
 20. The apparatus of claim 18, furthercomprising a potentiometer coupled between the first stage and thesecond stage, wherein the potentiometer is operable to measure themovement of the second stage relative to the first stage.